Off-pump extraanatomic aortic bypass for the treatment of complex aortic coarctation and hypoplastic aortic arch

BACKGROUND: Despite advances in surgical and interventional techniques, the optimal surgical treatment of severe aortic (re) coarctation and hypoplastic aortic arch is still controversial. Anatomic repair may require extensive dissection, cardiopulmonary bypass, and deep hypothermic circulatory arrest with their inherent risks. The aim of this study was to analyze the outcome of off-pump extraanatomic aortic bypass as a surgical alternative to local repair. METHODS: From February 2000 to December 2005, ten consecutive patients (median age 20 years; range, 11 to 38 years) with severe aortic (re) coarctation (n = 4) and (or) hypoplastic aortic arch (n = 7) underwent off-pump extraanatomic aortic bypass through median sternotomy. All but three patients had undergone previous surgery for coarctation and angioplasty or stenting. Three patients underwent concomitant replacement of the ascending aorta because of an aneurysm using cardiopulmonary bypass. RESULTS: Postoperative hospital course was uneventful in all patients. There was no perioperative mortality or significant morbidity. During a mean follow-up of 48 +/- 22 months no patient required additional procedures. All patients were free of symptoms; no patient showed signs of heart failure after follow-up. At last follow-up, no patient presented with claudication, nor any patient experienced orthostatic problems due to a steal phenomenon. During follow-up, hypertension resolved in all patients with residual mild hypertension in two patients. CONCLUSIONS: Off-pump extraanatomic aortic bypass is an attractive treatment option for complex aortic (re) coarctation and hypoplastic aortic arch. Perioperative risks are minimized, hypertension is influenced favorably, and midterm survival is event-free.

Severe structural damage of the seemingly non-diseased infrarenal aortic aneurysm neck

OBJECTIVE: The success of open and endovascular repair of abdominal aortic aneurysms (AAA) is hampered by postoperative dilatation of the anatomical neck of the AAA, which is used for graft attachment. The purpose of this study was to determine whether the macroscopically non-diseased infrarenal aortic neck of AAA is histologically and biochemically altered at the time of operative repair. METHODS: We harvested full-thickness aortic wall samples as longitudinal stripes spanning from AAA neck to aneurysmal sac in 22 consecutive patients undergoing open surgical AAA repair. Control tissue was obtained from five organ donors and five deceased subjects undergoing autopsy without evidence of aneurysmal disease. We assessed aortic media thickness, number of intact elastic lamellar units, media destruction, and neovascularization grade and performed immunohistochemistry for matrix metalloproteinase (MMP)-9 and phosphorylated c-Jun N-terminal kinase (p-JNK). MMP-9 and p-JNK protein expressions were quantified using Western Blots. RESULTS: The median thickness of the aortic media was 1150 mum in control tissue (range, 1000-1300), 510 mum in aortic necks (250-900), and 200 mum in aortic sacs (50-500, P from nonparametric test for trend <.001). The number of intact elastic lamellar units was 33 in controls (range, 33-55), 12 in aortic necks (0-31) and three in aortic sacs (0-10, P < .001). The expression of MMP-9 and p-JNK as assessed by Western Blots (P = .007 and .061, respectively) and zymography (P for trend <.001) were up regulated in both the AAA neck and sac compared with controls. Except for p-JNK expression, differences between tissues were similar after the adjustment for age, gender, and type of sampling. CONCLUSION: The seemingly non-diseased infrarenal AAA neck in patients with AAA undergoing surgical repair shows histological signs of destruction and upregulation of potential drug targets.

Simulation of four stroke engine cycle for a 4 - valve pentroof engine in KIVA 3VR2

The main purpose of this project is to understand the process of engine simulation using the open source CFD code called KIVA. This report mainly discusses the simulation of the 4-valve Pentroof engine through KIVA 3VR2. KIVA is an open source FORTRAN code which is used to solve the fluid flow field in the engines with the transient 2D and 3D chemically reactive flow with spray. It also focuses on the complete procedure to simulate an engine cycle starting from pre- processing until the final results. This report will serve a handbook for the using the KIVA code.

The diagnostic value of a treadmill test in predicting lumbar spinal stenosis

Lumbar spinal stenosis is a frequent indication for spinal surgery. The predictive quality of treadmill testing and MRI for diagnostic verification is not yet clearly defined. Aim of the current study was to assess correlations between treadmill testing and MRI findings in the lumbar spine. Twenty-five patients with lumbar spinal stenosis were prospectively examined. Treadmill tests were performed and the area of the dural sac and neuroforamina was examined with MRI for the narrowest spinal segment. VAS and ODI were used for clinical assessment. The median age of the patients was 67 years. In the narrowest spinal segment the median area of the dural sac was 91 mm(2). The median ODI was 66 per cent. The median walking distance in the treadmill test was 70 m. The distance reached in the treadmill test correlated with the area of the dural sac (Spearman's rho = 0.53) and ODI (rho = -0.51), but not with the area of the neuroforamina and VAS. The distance reached in the treadmill test predicts the grade of stenosis in MRI but has a limited diagnostic importance for the level of clinical symptoms in lumbar spinal stenosis.

Salivary stones and stenosis. A comprehensive classification

INTRODUCTION: Sialendoscopy and sialoMRI enables diagnosis of salivary gland obstructive pathologies, such as lithiasis, stenosis, and dilatations. Therefore, a classification of these pathologies is needed, allowing large series comparisons, for better diagnosis and treatment of salivary pathologies. MATERIAL AND METHODS: With help from people from the European Sialendoscopy Training Center (ESTC), the results of sialographies, sialoMRI and sialendoscopies, a comprehensive classification of obstructive salivary pathologies is described, based on the absence or presence of lithiasis (L), stenosis (S), and dilatation (D) ("LSD" classification). DISCUSSION: It appears that a classification of salivary gland obstructive pathologies should be described. We hope it will be widely used and of course criticized to be improved and to compare the results of salivary gland diagnostic methods, such as sialography and sialendoscopy, and also the results and indications for salivary gland therapeutic methods, such as lithotripsy, sialendoscopy, and/or open surgery.

DEVELOPMENT OF A PREDICTIVE COMBUSTION MODEL OF A SPARK IGNITED ENGINE WITH GASOLINE DIRECT INJECTION, VARIABLE VALVE TIMING, DURATION AND LIFT TECHNOLOGIES

There is a need by engine manufactures for computationally efficient and accurate predictive combustion modeling tools for integration in engine simulation software for the assessment of combustion system hardware designs and early development of engine calibrations. This thesis discusses the process for the development and validation of a combustion modeling tool for Gasoline Direct Injected Spark Ignited Engine with variable valve timing, lift and duration valvetrain hardware from experimental data. Data was correlated and regressed from accepted methods for calculating the turbulent flow and flame propagation characteristics for an internal combustion engine. A non-linear regression modeling method was utilized to develop a combustion model to determine the fuel mass burn rate at multiple points during the combustion process. The computational fluid dynamic software Converge ©, was used to simulate and correlate the 3-D combustion system, port and piston geometry to the turbulent flow development within the cylinder to properly predict the experimental data turbulent flow parameters through the intake, compression and expansion processes. The engine simulation software GT-Power © is then used to determine the 1-D flow characteristics of the engine hardware being tested to correlate the regressed combustion modeling tool to experimental data to determine accuracy. The results of the combustion modeling tool show accurate trends capturing the combustion sensitivities to turbulent flow, thermodynamic and internal residual effects with changes in intake and exhaust valve timing, lift and duration.

Prospective, intraindividual comparison of MRI versus MDCT for endoleak detection after endovascular repair of abdominal aortic aneurysms

This study compares MRI and MDCT for endoleak detection after endovascular repair of abdominal aortic aneurysms (EVAR). Forty-three patients with previous EVAR underwent both MRI (2D T1-FFE unenhanced and contrast-enhanced; 3D triphasic contrast-enhanced) and 16-slice MDCT (unenhanced and biphasic contrast-enhanced) within 1 week of each other for endoleak detection. MRI was performed by using a high-relaxivity contrast medium (gadobenate dimeglumine, MultiHance). Two blinded, independent observers evaluated MRI and MDCT separately. Consensus reading of MRI and MDCT studies was defined as reference standard. Sensitivity, specificity, and accuracy were calculated and Cohen's k statistics were used to estimate agreement between readers. Twenty endoleaks were detected in 18 patients at consensus reading (12 type II and 8 indeterminate endoleaks). Sensitivity, specificity, and accuracy for endoleak detection were 100%, 92%, and 96%, respectively, for reader 1 (95%, 81%, 87% for reader 2) for MRI and 55%, 100%, and 80% for reader 1 (60%, 100%, 82% for reader 2) for MDCT. Interobserver agreement was excellent for MDCT (k = 0.96) and good for MRI (k = 0.81). MRI with the use of a high-relaxivity contrast agent is significantly superior in the detection of endoleaks after EVAR compared with MDCT. MRI may therefore become the preferred technique for patient follow-up after EVAR.

MR findings of endocardial fibroelastosis in children

BACKGROUND: Endocardial fibroelastosis (EFE) is characterized by a diffuse white fibrous tissue lining the endocardium. The diagnosis is difficult to establish because clinical symptoms and electrocardiographic findings are nonspecific. Surgical resection of EFE requires the establishment of the diagnosis and delineation of the extent of the fibrotic changes. OBJECTIVE: To describe the use of MRI in the assessment of EFE in children. MATERIALS AND METHODS: Three children after surgery for aortic stenosis who were suspected of having EFE were evaluated by echocardiography and MRI. The MR evaluation consisted of black-blood, triple IR, bright-blood, perfusion and myocardial delayed-enhancement sequences. EFE was confirmed at surgery in all patients. RESULTS: Echocardiograms demonstrated vigorous systolic function but substantial diastolic dysfunction of the left ventricle in all. Mild endocardial brightening of the anterior septum, anterior wall, or papillary muscles was present in two. No study was thought to be diagnostic of endocardial fibrosis. On MRI EFE manifested at the endocardial surface as a rim of hypointense signal in the perfusion sequences and as a rim of hyperintense signal in the myocardial delayed-enhancement sequences. The black-blood, triple IR, and bright-blood sequences were not diagnostic. CONCLUSION: The diagnosis of EFE is difficult to establish by echocardiography. MRI using perfusion and myocardial delayed enhancement can be useful in establishing the diagnosis.

Thoracic endovascular aortic repair: impact of urgency on outcome and quality of life

OBJECTIVES: Endovascular repair of the descending thoracic aorta is a very promising technique in elective and, particularly, emergency situations. This study assessed the impact of urgency of the procedure on outcome and mid-term quality of life in surviving patients. METHODS: Post hoc analysis of prospectively collected data of 58 consecutive patients (January 2001-December 2005) with surgical pathologies of the descending thoracic aorta treated by endovascular means. Six patients were excluded due to recent operations on the ascending aorta before thoracic endovascular repair. The remaining patients (n=52) were 69+/-10 years old, and 43 were men (83%). Twenty-seven had been treated electively, and 25 for emergency indications. Reasons for emergency were acute type B aortic dissections with or without malperfusion syndrome in 14, and aortic ruptures in 11 cases. Follow-up was 29+/-16 months. Endpoints were perioperative and late morbidity and mortality rates and long-term quality of life as assessed by the short form health survey (SF-36) and Hospital Anxiety and Depression Scale questionnaires. RESULTS: Cohorts were comparable regarding age, sex, cardiovascular risk factors, and comorbidities. Perioperative mortality was somewhat higher in emergency cases (12% vs 4%, p=0.34). Paraplegia occurred in one patient in each cohort (4%). Overall quality of life after two and a half years was similar in both treatment cohorts: 72 (58-124) after emergency, and 85 (61-105) after elective endovascular aortic repair (p=0.98). Normal scores range from 85 to 115. Anxiety and depression scores were in the normal range and comparable. CONCLUSIONS: Thoracic endovascular aortic repair is an excellent and safe treatment option for the diseased descending aorta, particularly in emergency situations. Early morbidity and mortality rates can be kept very low. Mid-term quality of life was not affected by the urgency of the procedure. Similarly, mid-term anxiety and depression scores were not increased after emergency situations.

Outcome and quality of life after surgical and endovascular treatment of descending aortic lesions

BACKGROUND: Thoracic endovascular aortic repair (TEVAR) represents an attractive alternative to open aortic repair (OAR). The aim of this study was to assess outcome and quality of life in patients treated either by TEVAR or OAR for diseased descending thoracic aorta. METHODS: A post hoc analysis of a prospectively collected consecutive series of 136 patients presenting with surgical diseases of the descending aorta between January 2001 and December 2005 was conducted. Fourteen patients were excluded because of involvement of the ascending aorta. Assessed treatment cohorts were TEVAR (n = 52) and OAR (n = 70). Mean follow-up was 34 +/- 18 months. End points were perioperative and late mortality rates and long-term quality of life as assessed by the Short Form Health Survey (SF-36) and Hospital Anxiety and Depression Score questionnaires. RESULTS: Mean age was significantly higher in TEVAR patients (69 +/- 10 years versus 62 +/- 15 years; p = 0.002). Perioperative mortality rates were 9% (OAR) and 8% (TEVAR), respectively (p = 0.254). Accordingly, cumulative long-term mortality rates were similar in both cohorts. Overall quality-of-life scores were 93 (63-110, OAR) and 83 (60-112, TEVAR), respectively. Normal quality-of-life scores range from 85 to 115. Anxiety and depression scores were not increased after open surgery. CONCLUSIONS: Thoracic endovascular aortic repair and OAR both provide excellent long-term results in treatment of thoracic aortic disease. Long-term quality of life, however, is reduced after thoracic aortic repair. Interestingly, TEVAR patients did not score higher in overall quality of life despite all advantages of minimized access trauma. Similarly, anxiety and depression scores are not reduced by TEVAR, possibly reflecting a certain caution against the new technology.

Outcome and quality of life in patients treated for abdominal aortic aneurysms: a single center experience

BACKGROUND: Durability of protection and long-term quality of life (QoL) are critical outcome parameters of abdominal aortic aneurysm (AAA) repair. The aim of the present study was to compare results of endovascular and open aneurysm repair (EVAR and OR) with adjusted standard populations, including stratification for urgency of presentation. METHODS: Retrospective analysis of prospectively collected data of 401 consecutive patients presenting with AAA between January 1998 and December 2002. Cross-sectional follow up was 58 +/- 29 months. Patients were grouped into three cohorts: elective EVAR (n = 68), elective OR (n = 244), and emergency OR (including symptomatic and ruptured AAA, n = 89). Endpoints were perioperative (i.e., 30 days or in-hospital) and late mortality rates, as well as long-term QoL as assessed by the Short Form health survey questionnaire (SF-36). RESULTS: Mean age was lower in the elective OR cohort (66 +/- 10 years) than in the EVAR cohort (72 +/- 7 years; p < .05). Perioperative mortality rates were 4.4%, 0.4%, and 10.1%, for the EVAR, elective OR, and emergency OR cohorts, respectively (p < .05). Corresponding cumulative survival rates after 4 years were 67%, 89%, and 69%, respectively. Long-term QoL SF-36 scores were in all cohorts similar to age- and gender-adjusted standard populations, which score between 85 and 115: 99.6 +/- 35.8 (EVAR), 101.3 +/- 32.4 (elective OR), and 100.4 +/- 36.5 (emergency OR). CONCLUSIONS: Long-term QoL is not permanently impaired after AAA repair, but returns in long-term survivors to what would be expected in a standard population. In this respect, differences were found neither between EVAR and OR, nor between elective and emergency repair. Perioperative mortality rates were highest in patients undergoing emergency OR. The outlook for such patients after the perioperative period, however, was similar to that for patients undergoing elective repair.